哈希+枚举

• 第一层枚举长度，第二层从1枚举到n，map存哈希值

• 如果当前长度下，没有字符串有公共前缀，那就break，因为后面的长度都不可能有了

bool M1;
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define deb(x) cerr<<"l: "<<__LINE__<<"  "<<#x<<"="<<x<<'\n'
#define look_memory cerr<<abs(&M2-&M1)/1024.0/1024<<"MB\n"

namespace syr
{
	const ll N = 1e6+10;
	const ll V = 1e7+10;
	const ull M = 13;
	char c;
	ll n, ax, ans;
	ll len[N], v[V];
	ull t[N];
	unordered_map <ull, ll> m;
	string s[N];
	void work()
	{
		cin>>n;
		c = getchar();
		for (ll i=1; i<=n; i++) {
			s[i] = " ";
			while (c=getchar()) {
				if (c=='\n') break;
				s[i] += c;
				len[i]++;
			}
			ax = max(ax, len[i]);
		}
		ans = ax;
		for (ll i=1; i<=ax; i++) {
			m.clear();
			for (ll j=1; j<=n; j++) {
				if (len[j]<i) continue;
				t[j] = t[j]*M + s[j][i]-'a'+1;
				m[t[j]]++;
				v[i] = max(v[i], m[t[j]]);
			}
			if (v[i]==1) break;
			ans = max(ans, i*v[i]); 
		}
		cout<<ans<<'\n';
	}
}

bool M2;

int main()
{
//	cin.tie(0)->sync_with_stdio(0);
	look_memory;
	syr::work();
	return 0;
}